Ultrasonic diagnosis device

ABSTRACT

The purpose of the present invention is to improve the accuracy of Doppler measurements. An ultrasonic diagnosis device comprises: a transmission unit  12  for transmitting, through a probe  14 , an ultrasonic wave for each of a plurality of transmit beams formed at different positions or in different directions; a reception unit  20  for receiving, through the probe  14 , an ultrasonic wave for each receive beam included in a receive beam set formed to correspond to each transmit beam; a Doppler processing unit  24  for determining a Doppler measurement for each of the receive beams; and a combining/selecting unit  26  for combining a first Doppler measurement determined for a first receive beam belonging to a receive beam set formed to correspond to a first transmit beam and a second Doppler measurement determined for a second receive beam belonging to a receive beam set formed to correspond to a second transmit beam when the first receive beam and the second receive beam are in a predetermined positional relationship.

TECHNICAL FIELD

The present invention relates to an ultrasonic diagnostic device, andparticularly to an ultrasonic diagnostic device that forms a pluralityof received beams at different positions or in different directions fora single transmitting beam.

BACKGROUND

Ultrasonic diagnostic devices designed for measuring the velocity ofblood flow of an examinee using a Doppler technique are widely used.These ultrasonic diagnostic devices include a multiline ultrasonicdiagnostic device that transmits ultrasound waves for one transmittingbeam, and, based on ultrasound waves received from each direction of aplurality of received beams having different positions or directions,performs Doppler measurement.

The multiline ultrasonic diagnostic devices described in PatentDocuments 1 and 2 transmit ultrasound waves with respect to a pluralityof parallel transmitting beams. For each transmitting beam, an ensembleof a plurality of parallel received beams (a set of received beams) isformed, and ultrasound waves are received for each received beam. Areceived beam outside each ensemble overlaps a received beam outside theadjacent ensemble.

When received beams that belong to an ensemble formed corresponding toone transmitting beam overlap received beams that belong to an ensembleformed corresponding to another transmitting beam, the Doppler frequencyor velocity is determined for one received beam direction, based on eachof received data items obtained for the overlapping received beams.

CITATION LIST Patent Literature

[Patent Document 1] JP 2010-511420 A

[Patent Document 2] U.S. Pat. No. 8,475,380 B2, description

SUMMARY Technical Problem

In general, the accuracy of Doppler measurement depends on a positionalrelationship between transmitting beams and received beams. In Dopplermeasurement performed by forming a plurality of received beams atdifferent positions or in different directions for one transmittingbeam, the accuracy of Doppler measurement values, such as Dopplerfrequency and velocity, may be reduced depending on the positionalrelationship between the received beams and the transmitting beams.

An object of the invention is to increase the accuracy of Dopplermeasurement values.

Solution to Problem

In accordance with an aspect of the invention, an ultrasonic diagnosticdevice includes a transmitter unit configured to transmit ultrasoundwaves for each of a plurality of transmitting beams formed at differentpositions or in different directions, a receiver unit configured toreceive ultrasound waves concerning each of a plurality of receivedbeams in each set of received beams, the plurality of received beamsbeing formed at different positions or in different directions, the eachset of received beams being formed corresponding to each transmittingbeam, a Doppler processing unit configured to determine a Dopplermeasurement value for each of the received beams based on the ultrasoundwaves received by the receiver unit, and a combining unit configured tocombine, when a first received beam that belongs to a set of receivedbeams formed corresponding to a first transmitting beam and a secondreceived beam that belongs to a set of received beams formedcorresponding to a second transmitting beam are in a predeterminedpositional relationship, a first Doppler measurement value determinedfor the first received beam and a second Doppler measurement valuedetermined for the second received beam.

In embodiments of the present invention, when the first received beamcorresponding to the first transmitting beam and the second receivedbeam corresponding to the second transmitting beam are in apredetermined positional relationship, the first Doppler measurementvalue determined for the first received beam and the second Dopplermeasurement value determined for the second received beam are combined.This approach can determine correct measurement values based on Dopplermeasurement values determined for two sets of received beams. TheDoppler measurement values in the embodiments of the present inventioninclude, for example, measurement values of Doppler frequencies andmeasurement values of velocities.

In preferred embodiments, the combining unit is configured toweight-combine the first Doppler measurement value and the secondDoppler measurement value, with weighting in accordance with apositional relationship between the first transmitting beam and thefirst received beam and a positional relationship between the secondtransmitting beam and the second received beam.

In general, the accuracy of Doppler measurement values depends on thepositional relationship between transmitting beams and received beams.For example, as a distance between a transmitting beam and a receivedbeam becomes smaller, the accuracy of Doppler measurement values whichis determined becomes higher. Further, as the difference between thedirection of a transmitting beam and the direction of a received beambecomes closer to 180°, for example, the accuracy of Doppler measurementvalues which is determined is higher. In embodiments of the presentinvention, the first Doppler measurement value and the second Dopplermeasurement value are weight-combined appropriately in accordance withthe positional relationship between the transmitting beam and thereceived beam.

In preferred embodiments, the transmitter unit is configured to transmitultrasound waves a plurality of times for one transmitting beam, and theDoppler processing unit is configured to determine the Dopplermeasurement value for each of the received beams based on ultrasoundwaves received by the receiver unit a plurality of times. The ultrasonicdiagnostic device further includes a variation determining unitconfigured to determine, for each of the received beams, a variationlevel based on an amount that contributes to the Doppler measurementvalue, concerning the ultrasound waves received by the receiver unit aplurality of times for each of the received beams. The combining unit isconfigured to weight-combine the first Doppler measurement value and thesecond Doppler measurement value, with weighting in accordance with thevariation level determined for each of the first Doppler measurementvalue and the second Doppler measurement value.

In embodiments of the present invention, the Doppler processing unitdetermines a Doppler measurement value for each received beam based onultrasound waves received by the receiver unit a plurality of times.Further, the variation determining unit determines a variation level foreach received beam. In general, as the variation level becomes smaller,the accuracy of Doppler measurement value which is determined becomeshigher. According to embodiments of the present invention, the firstDoppler measurement value and the second Doppler measurement value areappropriately weight-combined, with weighting in accordance with thevariation level concerning an amount of contribution to the Dopplermeasurement values.

In accordance with another aspect of the invention, an ultrasonicdiagnostic device includes a transmitter unit configured to transmitultrasound waves for each of a plurality of transmitting beams formed atdifferent positions or in different directions, a receiver unitconfigured to receive ultrasound waves concerning each of a plurality ofreceived beams in each set of received beams, the plurality of receivedbeams being formed at different positions or in different directions,the each set of received beams being formed corresponding to eachtransmitting beam, a Doppler processing unit configured to determine aDoppler measurement value for each of the received beams based on theultrasound waves received by the receiver unit, and a selecting unitconfigure to select, when a first received beam that belongs to a set ofreceived beams formed corresponding to a first transmitting beam and asecond received beam that belongs to a set of received beams formedcorresponding to a second transmitting beam are in a predeterminedpositional relationship, either a first Doppler measurement determinedfor the first received beam or a second Doppler measurement determinedfor the second received beam, based on an evaluation condition for eachDoppler measurement value.

In embodiments of the present invention, when the first received beamcorresponding to the first transmitting beam and the second receivedbeam corresponding to the second transmitting beam are in apredetermined positional relationship, one of the first Dopplermeasurement value determined for the first received beam and the secondDoppler measurement value determined for the second received beam isselected based on an evaluation condition for each Doppler measurementvalue. As a result, one of the Doppler measurement values determined fortwo received beam sets is appropriately selected.

In preferred embodiments, the selecting unit is configured to selecteither the first Doppler measurement value or the second Dopplermeasurement value based on a positional relationship between the firsttransmitting beam and the first received beam and a positionalrelationship between the second transmitting beam and the secondreceived beam.

In general, the accuracy of Doppler measurement values depends on thepositional relationship between a transmitting beam and a received beam.According to embodiments of the present invention, one of the firstDoppler measurement value or the second Doppler measurement value isselected appropriately based on the positional relationship between thetransmitting beam and the received beam.

In preferred embodiments, the transmitter unit is configured to transmitultrasound waves a plurality of times for one transmitting beam, and theDoppler processing unit is configured to determine the Dopplermeasurement value for each of the received beams based on the ultrasoundwaves received by the receiver unit a plurality of times. The ultrasonicdiagnostic device further comprises a variation determining unitconfigured to determine, for each of the received beams, a variationlevel based on an amount that contributes to the Doppler measurementvalue, concerning the ultrasound waves received by the receiver unit aplurality of times for each of the received beams. The selecting unit isconfigured to select either the first Doppler measurement value or thesecond Doppler measurement value based on the variation level determinedfor each of the first Doppler measurement value and the second Dopplermeasurement value.

In embodiments of the present invention, the Doppler processing unitdetermines a Doppler measurement value for each received beam based onultrasound waves received by the receiver unit a plurality of times.Further, the variation determination unit determines the variation levelfor each received beam. The accuracy of Doppler measurement values whichis determined generally becomes higher as the variation level becomessmaller. According to embodiments of the present invention, one of thefirst Doppler measurement value and the second Doppler measurement valueis selected appropriately based on the variation level concerning theamount of contribution to the Doppler measurement value.

Advantageous Effects of Invention

According to embodiments of the present invention, the accuracy ofDoppler measurement values can be increased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating the structure of an ultrasonicdiagnostic device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example positional relationshipbetween transmitting beams and received beams when linear scanning isperformed.

FIG. 3 is a diagram illustrating the structure of a Doppler processingunit.

FIG. 4 is a diagram illustrating an example positional relationshipbetween transmitting beams and received beams when sector scanning isperformed.

DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates the structure of an ultrasonic diagnostic deviceaccording to an embodiment of the present invention. The ultrasonicdiagnostic device executes measurement in B-mode and measurement inDoppler mode in time division. The ultrasonic diagnostic devicetransmits and receives ultrasound waves to and from an examinee 18. InB-mode, the ultrasonic diagnostic device displays a tomographic imagebased on ultrasound waves received from the examinee 18. In Dopplermode, the ultrasonic diagnostic device measures and displays blood flowvelocity within the examinee 18 based on Doppler frequencies ofultrasound waves received from the examinee 18. The blood flow velocityis a vector having a direction and a magnitude and is displayed withgraphics such as arrows, a combination of color and luminance, or twocomponent values.

The structure of the ultrasonic diagnostic device, and processing to beexecuted by the ultrasonic diagnostic device will be described. A probe14 is in contact with a body surface of the examinee 18. In thefollowing description, the direction along the surface of the examinee18 is referred to as an x-axis direction, and the directioncorresponding to the depth direction of the examinee 18 is referred toas a y-axis positive direction. The probe 14 includes a plurality oftransducer elements 16. A transmitter unit 12 outputs transmittingsignals to each transducer element 16 of the probe 14 under control of abeam control unit 10. As a result, ultrasound waves are transmitted fromthe probe 14. The beam control unit 10 controls the transmitter unit 12to form transmitting beams in the probe 14 and scan the transmittingbeams with respect to the examinee 18. More specifically, thetransmitter unit 12, under control of the beam control unit 10, formsthe transmitting beams in the probe 14 while adjusting the delay timeand the level of each transmitting signal and scans the transmittingbeams with respect to the examinee 18. In this embodiment, thetransmitting beams are directed to the y-axis positive direction andscanned linearly in the x-axis direction.

Receiving ultrasound waves reflected within the examinee 18, eachtransducer element 16 of the probe 14 outputs electrical signals inaccordance with the received ultrasound waves to a receiver unit 20. Thereceiver unit 20, under control of the beam control unit 10, appliesamplification, orthogonal detection, and other processing to thereceived signals output from each transducer element 16. The receiverunit 20 thus generates received baseband signals of a plurality ofchannels corresponding to the plurality of transducer elements 16, andtemporarily stores each received baseband signal for phase alignment andsummation. Each received baseband signal includes an in-phase componentI and an orthogonal component Q. The argument of a vector (I, Q) in anIQ plane represents a phase angle of the received signal, and avariation quantity of the argument of the vector (I, Q) per unit timerepresents a Doppler frequency.

A phase alignment and summation unit 22 applies phase alignment andsummation to the received baseband signals of a plurality of channelsgenerated in the receiver unit 20 to generate received data. The probe14 thus forms the received beams and generates the received data basedon the ultrasound waves received along the received beams. The receiveddata, similar to the received baseband signals, include an in-phasecomponent and an orthogonal component. The phase alignment and summationunit 22 outputs the received data to a tomographic image generating unit30 under operation in the B-mode, and outputs the received data to aDoppler processing unit 24 under operation in the Doppler mode.

The operation in the B-mode will be described. The phase alignment andsummation unit 22 applies phase alignment and summation to the receivedbaseband signals of a plurality of channels generated by the receiverunit 20. The phase alignment and summation unit 22 thereby generatesreceived data based on ultrasound waves received along the receivedbeams in the same direction as the direction of scanned transmittingbeams, and outputs the received data to the tomographic image generatingunit 30. The phase alignment and summation unit 22 thus generates eachreceived data item based on ultrasound waves received from eachdirection of the received beam scanned within the examinee 18, andoutputs the received data to the tomographic image generating unit 30.The tomographic image generating unit 30 generates tomographic imagedata based on the received data obtained for each received beamdirection, and outputs the tomographic image data to an image combiningunit 32. One tomographic image data item based on the transmitting beamand the received beam for one scanning corresponds to image data of oneframe, which, in turn, corresponds to one tomographic image. The beamcontrol unit 10, the transmitter unit 12, the probe 14, the receiverunit 20, the phase alignment and summation unit 22, and the tomographicimage generating unit 30 sequentially generate tomographic image data inconjunction with repeated scanning of the transmitting beams and thereceived beams, and output each tomographic image data item to the imagecombining unit 32. A plurality of tomographic image data items generatedon a time series basis form motion image data.

The operation in the Doppler mode will be now described. In the Dopplermode, ultrasonic pulses are transmitted a plurality of N times atrepeated time intervals T for one transmitting beam direction. Thereceiver unit 20 generates received baseband signals in accordance witheach received ultrasonic pulse reflected within the examinee 18.

The phase alignment and summation unit 22 executes processing forforming a plurality of received beams for one time transmission ofultrasonic pulse. More specifically, the phase alignment and summationunit 22 applies phase alignment and summation to the received basebandsignals of a plurality of channels generated by the receiver unit 20, toform a plurality of received beams having the same direction as thedirection of the transmitting beam and arranged in parallel to eachother. The phase alignment and summation unit 22 then generates receiveddata based on the ultrasound waves received along each received beam.The phase alignment and summation unit 22 subsequently outputs eachreceived data item to the Doppler processing unit 24.

FIG. 2 illustrates an example positional relationship between thetransmitting beams and the received beams. As illustrated in thisdrawing, the transmitting beams T0, T1, and T2 are formed toward thedepth direction (y-axis positive direction). In the example in FIG.2(a), at the position with depth y=y0, eight received beams R0 to R7 areformed at equal intervals toward the y-axis negative direction with thetransmitting beam T0 as their center.

The phase alignment and summation unit 22 generates, concerning each ofthe ultrasonic pulses transmitted and received for N times, eachreceived data item based on the ultrasound waves received along each ofa plurality of received beams.

When M received beams are formed, N received data items are generatedfor each of the M received beams, and received data items in the numberof (M·N) are output from the phase alignment and summation unit 22 tothe Doppler processing unit 24. In the example illustrated in FIG. 2(a),with M=8, the received beams R0 to R7 are formed, and received dataitems in the number of (8·N) are output from the phase alignment andsummation unit 22 to the Doppler processing unit 24.

As described above, the transmitting beams are scanned linearly in thex-axis direction. The phase alignment and summation unit 22 generates Nreceived data items for each of M received beams, with respect to eachposition of the transmitting beams linearly scanned in the x-axisdirection, and outputs the generated received data to the Dopplerprocessing unit 24.

In the example illustrated in FIG. 2(b), the transmitting beam isscanned in the x-axis direction, and the transmitting beam T1 is formedat a position toward the right from the transmitting beam T0, and eightreceived beams Q0 to Q7 are formed toward the y-axis negative directionat equal intervals, with the transmitting beam T1 as their center, atthe position with the depth y=y0. The phase alignment and summation unit22 performs processing similar to the processing with respect to thereceived beam R0 to R7 illustrated in FIG. 2(a). The phase alignment andsummation unit 22 thereby generates each received data item based onultrasound waves received along each of the received beams Q0 to Q7, foreach of the ultrasonic pulses transmitted and received for N times, andoutputs each received data item that is generated to the Dopplerprocessing unit 24.

In the example illustrated in FIG. 2(c), the transmitting beam isscanned in the x-axis direction, and the transmitting beam T2 is formedat a position toward the right from the transmitting beam T1, and eightreceived beams P0 to P7 are formed toward the y-axis negative directionat equal intervals, with the transmitting beam T2 as their center, atthe position with the depth y=y0. The phase alignment and summation unit22 performs processing similar to the processing with respect to thereceived beam R0 to R7 illustrated in FIG. 2(a). The phase alignment andsummation unit 22 thereby generates each received data item based onultrasound waves received along each of the received beams P0 to P7, foreach of the ultrasonic pulses transmitted and received for N times, andoutputs each received data item that is generated to the Dopplerprocessing unit 24.

FIG. 3 illustrates the structure of the Doppler processing unit 24. TheDoppler processing unit 24 includes an MTI filter processing unit 36, anautocorrelation processing unit 38, and a velocity calculation unit 40,and executes the following Doppler operation processing with respect tothe N received data items obtained for one received beam to obtainvelocity measurement values. MTI is an abbreviation of Moving TargetIndication.

The MTI filter processing unit 36 reduces or eliminates, from Dopplerfrequency components of the received data, components having a frequencywhich is equal to or less than a predetermined cutoff frequency. Thereceived data item includes an in-phase component and an orthogonalcomponent, each including a Doppler frequency component. The MTI filterprocessing unit 36 applies processing for reducing or eliminating aDoppler frequency component having a frequency equal to or less than thecutoff frequency, to each of the in-phase component and the orthogonalcomponent contained in the received data.

The autocorrelation processing unit 38 auto-correlates the N receiveddata items. The received data for the k-th (k=1 to N) ultrasonic pulse,among the N ultrasonic pulses transmitted at the repeated time intervalsT, is represented by the following Formula 1:

z(y,k)=I(y,k)+j·Q(y,k)  [Formula 1]

In Formula 1, y is a coordinate value in the depth direction, I(y, k)indicates an in-phase component and Q(y, k) indicates an orthogonalcomponent, and j is the imaginary unit. The autocorrelation processingunit 38 determines, in accordance with the following Formula 2, anautocorrelation value S(y) for N received data items z(y, 1), z(y, 2), .. . z(y, N), and outputs the result to the velocity calculation unit 40.

$\begin{matrix}{{S(y)} = {\sum\limits_{k = 1}^{N - 1}\; {{z\left( {y,k} \right)} \cdot {z\left( {y,{k + 1}} \right)}^{*}}}} & \left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In the above formula, the superscript “*” indicates a complex conjugate.The velocity calculation unit 40 obtains velocity measurement valuesv(y) according to the following Formula 3 using a real part Re[S(y)] andan imaginary part Im[S(y)] of the autocorrelation value S(y) obtained bythe autocorrelation processing unit 38 and outputs the result to acombining/selecting unit 26.

$\begin{matrix}{{v(y)} = {{\frac{c}{2f_{0}} \cdot \frac{1}{2\pi \; T}}{\arctan \left\lbrack \frac{{Im}\left\lbrack {S(y)} \right\rbrack}{{Re}\left\lbrack {S(y)} \right\rbrack} \right\rbrack}}} & \left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In Formula 3, c is a propagation velocity of an ultrasound wavepropagating within the examinee 18, and f₀ is a frequency of anultrasound wave transmitted and received at the probe 14. Of the rightside of Formula 3, a right part with respect to c/(2f₀) represents aDoppler frequency. The velocity measurement value v(y) represents ay-axis direction component of the blood flow velocity at the depth y.When the angle φ formed by the direction of the blood flow with respectto the y-axis is known, v(y)/cos φ is the blood flow velocity.

When it is not necessary to obtain absolute values of blood flowvelocity (values in MKSA system of unit, for example), such as whenmeasuring distribution of the blood flow velocity, the velocitymeasurement value may be obtained by multiplying the value obtained byFormula 3 by an arbitrary constant. Alternatively, in place of thevelocity measurement value, a Doppler frequency measurement valuecorresponding to the right part of c/(2f₀) in the right side of Formula3 may be used.

The Doppler processing unit 24, according to the processing describedabove, obtains a velocity measurement value for each of M received beamsformed with regard to one transmitting beam, and outputs the velocitymeasurement value obtained for each received beam to thecombining/selecting unit 26. The Doppler processing unit 24 furtherobtains a velocity measurement value for each of M received beams, withrespect to each position of the transmitting beam linearly scanned inthe x-axis direction, and outputs the result to the combining/selectingunit 26.

When any of M received beams formed for one of two adjacent transmittingbeams and any of M received beams formed for the other transmitting beamoverlap, the combining/selecting unit 26 combines the velocitymeasurement values obtained for each of the overlapping received beams.

Combining executed by the combining/selecting unit 26 will be describedwith reference to FIG. 2. As illustrated in FIGS. 2(a) and (b), of thereceived beams R0 to R7 formed with the transmitting beam T0 as theircenter, the received beam R5 to R7 are formed at positions respectivelycorresponding to the positions where the received beams Q0 to Q2, amongthe received beams Q0 to Q7 formed with the transmitting beam T1 astheir center, are formed. Further, as illustrated in FIGS. 2(b) and (c),of the received beams Q0 to Q7 formed with the transmitting beam T1 astheir center, the received beams Q5 to Q7 are formed at positionsrespectively corresponding to the positions where the received beams P0to P2, among the received beams P0 to P7 formed with the transmittingbeam T2 as their center, are formed.

The combining/selecting unit 26 obtains, concerning each of thepositions in the x-axis direction at the depth y=y0 of the receivedbeams R0 to R7, the received beams Q3 to Q7, and the received beams P3to P7, a combined measurement value that is a combined value of thevelocity measurement values. More specifically, the combining/selectingunit 26 obtains, concerning the 18 received beams to be observed, whichare the received beams R0 to R7, the received beams Q3 to Q7, and thereceived beams P3 to P7, combined measurement values v0 to v17sequentially from left to right. FIG. 2(d) indicates a relationshipbetween the positions in the x-axis direction and the combinedmeasurement values v0 to v17.

The combining/selecting unit 26 first determines the combinedmeasurement values v0 to v4 for the received beams R0 to R4 to be thesame values as the velocity measurement values output from the Dopplerprocessing unit 24, respectively. The combining/selecting unit 26 thenobtains the combined measurement values v5 to v7 for the received beamsR5 to R7 to be observed, according to Formula 4.

$\begin{matrix}\left\{ \begin{matrix}{{v\; 5} = {{w\; {5 \cdot {v\left( {R\; 5} \right)}}} + {\left( {1 - {w\; 5}} \right) \cdot {v\left( {Q\; 0} \right)}}}} \\{{v\; 6} = {{w\; {6 \cdot {v\left( {R\; 6} \right)}}} + {\left( {1 - {w\; 6}} \right) \cdot {v\left( {Q\; 1} \right)}}}} \\{{v\; 7} = {{w\; {7 \cdot {v\left( {R\; 7} \right)}}} + {\left( {1 - {w\; 7}} \right) \cdot {v\left( {Q\; 2} \right)}}}}\end{matrix} \right. & \left\lbrack {{Formula}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In Formula 4, v(R5) to v(R7) are velocity measurement values obtainedaccording to Formula 3 for the received beams R5 to R7, respectively, atthe depth y=y0. Further, v(Q0) to v(Q2) are velocity measurement valuesobtained according to Formula 3 for the received beams Q0 to Q2,respectively, at the depth y=y0, and w5 to w7 are weighting coefficientsdetermined for the received beams R5 to R7, respectively. The weightingcoefficient w is determined in accordance with a relationship of lengthsbetween an observing side transmitting and receiving distance between areceived beam to be observed and a transmitting beam corresponding tothe received beam, and a combining side transmitting and receivingdistance between a received beam to be combined and a transmitting beamcorresponding to the received beam. For example, when the observing sidetransmitting and receiving distance is greater than the combining sidetransmitting and receiving distance, the weighting coefficient w isdetermined within a range of 0<w<0.5. When the observing sidetransmitting and receiving distance is less than the combining sidetransmitting and receiving distance, the weighting coefficient w isdetermined within a range of 0.5<w<1. When the observing sidetransmitting and receiving distance is equal to the combining sidetransmitting and receiving distance, the weighting coefficient w isdetermined as w=0.5.

In the example illustrated in FIGS. 2(a) and (b), assuming that thedistance between received beams is D, the distance between the receivedbeam R5 and the transmitting beam T0 is 1.5D. The distance between thereceived beam Q0 and the transmitting beam T1 is 3.5D. As the observingside transmitting and receiving distance is therefore smaller than thecombining side transmitting and receiving distance, the weightingcoefficient w5 is determined within a range of 0.5<w5<1. Further, as thedistance between the received beam R6 and the transmitting beam T0 is2.5D and the distance between the received beam Q1 and the transmittingbeam T1 is also 2.5D, the observing side transmitting and receivingdistance and the combining side transmitting and receiving distance areequal to each other, and therefore the weighting coefficient w6 isdetermined to be 0.5. Further, the distance of the received beam R7 andthe transmitting beam T0 is 3.5D and the distance between the receivedbeam Q2 and the transmitting beam T1 is 1.5D. As the observing sidetransmitting and receiving distance is therefore greater than thecombining side transmitting and receiving distance, the weightingcoefficient w7 is determined within a range of 0<w7<0.5.

The combining/selecting unit 26 then determines the combined measurementvalues v8 and v9 for the received beams Q3 and Q4 to be the same valuesas the velocity measurement values, respectively, output from theDoppler processing unit 24. The combining/selecting 26 further obtainsthe combined measurement values v10 to v12 for the received beams Q5 toQ7 to be observed according to Formula 5.

$\begin{matrix}\left\{ \begin{matrix}{{v\; 10} = {{w\; {10 \cdot {v\left( {Q\; 5} \right)}}} + {\left( {1 - {w\; 10}} \right) \cdot {v\left( {P\; 0} \right)}}}} \\{{v\; 11} = {{w\; {11 \cdot {v\left( {Q\; 6} \right)}}} + {\left( {1 - {w\; 11}} \right) \cdot {v\left( {P\; 1} \right)}}}} \\{{v\; 12} = {{w\; {12 \cdot {v\left( {Q\; 7} \right)}}} + {\left( {1 - {w\; 12}} \right) \cdot {v\left( {P\; 2} \right)}}}}\end{matrix} \right. & \left\lbrack {{Formula}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In Formula 5, v(Q5) to v(Q7) are velocity measurement values obtainedaccording to Formula 3 for the received beams Q5 to Q7, respectively, atthe depth y=y0. Further, v(P0) to v(P2) are velocity measurement valuesobtained according to Formula 3 for the received beams P0 to P2 at thedepth y=y0. Also, w10 to w12 are weighting coefficients determined forthe received beams Q5 to Q7, respectively. Each weighting coefficient isdetermined based on the length relationship between the observing sidetransmitting and receiving distance and the combining side transmittingand receiving distance, similar to Formula 5.

In the example illustrated in FIGS. 2(b) and (c), assuming that thedistance between received beams is D, the distance between the receivedbeam Q5 and the transmitting beam T1 is 1.5D. The distance between thereceived beam P0 and the transmitting beam T2 is 3.5D. As the observingside transmitting and receiving distance is therefore smaller than thecombining side transmitting and receiving distance, the weightingcoefficient w10 is determined within a range of 0.5<w10<1. Further, asthe distance between the received beam Q6 and the transmitting beam T1is 2.5D and the distance between the received beam P1 and thetransmitting beam T2 is also 2.5D, the observing side transmitting andreceiving distance and the combining side transmitting and receivingdistance are equal to each other and the weighting coefficient w11 isdetermined to be 0.5. Further, the distance of the received beam Q7 andthe transmitting beam T1 is 3.5D and the distance between the receivedbeam P2 and the transmitting beam T2 is 1.5D. As the observing sidetransmitting and receiving distance is therefore greater than thecombining side transmitting and receiving distance, the weightingcoefficient w12 is determined within a range of 0<w12<0.5.

Finally, the combining/selecting unit 26 determines the combinedmeasurement values v13 to v17 for the received beams P3 to P7 to be assame values as the velocity measurement values output from the Dopplerprocessing unit 24, respectively.

When the first received beam that belongs to a set of received beamsformed corresponding to a transmitting beam to be observed (the firsttransmitting beam) and the second received beam that belongs to a set ofreceived beams formed corresponding to another transmitting beam (thesecond transmitting beam) overlap each other as described above, thecombining/selecting unit 26 combines the velocity measurement value asthe Doppler measurement value obtained for the first received beam andthe velocity measurement value as the second Doppler measurement valueobtained for the received beam, to obtain a measurement value for thetransmitting beam to be observed.

The combining/selecting unit 26 generates, based on the combinedmeasurement value obtained for each position (each depth) in the y-axisdirection and each position in the x-axis direction, velocitymeasurement data corresponding to xy coordinate values, and outputs thevelocity measurement data to a Doppler image generating unit 28.

The Doppler image generating unit 28 generates Doppler image data bytransforming the xy coordinate values to coordinates values of thedisplay screen, concerning the velocity measurement data. The Dopplerimage generating unit 28 may apply to the Doppler image data spacefilter processing for smoothing variations of pixel values in thedisplay screen direction. A Doppler image represented by the Dopplerimage data is, for example, a color Doppler image including pixelshaving colors determined based on the polarity of the combinedmeasurement value. Further, in the Doppler image, the luminance of eachpixel may be determined based on the magnitude of the combinedmeasurement value. The Doppler image generating unit 28 outputs theDoppler image data to the image combining unit 32.

The Doppler image generating unit 28 may also generate Doppler imagedata that represents the velocity measurement values by fillingpatterns, instead of colors. Alternatively, the Doppler image generatingunit 28 may generate numerical value image data representing thevelocity measurement values by numerical values and graphs, for example.

The beam control unit 10, the transmitter unit 12, the probe 14, thereceiver unit 20, the phase alignment and summation unit 22, the Dopplerprocessing unit 24, the combining/selecting unit 26, and the Dopplerimage generating unit 28 repeat scanning of the transmitting beam andeach received beam and sequentially generate the Doppler image data, andoutput each Doppler image data item to an image combining unit 32. Aplurality of Doppler image data items generated in time sequence formmotion image data.

The image combining unit 32, based on the tomographic image data outputfrom the tomographic image generating unit 30 and the Doppler image dataoutput from the Doppler image generating unit 28, superposes a Dopplerimage on a tomographic image to generate a tomographic/Doppler imagedata, and outputs the tomographic/Doppler image data to a display unit34. The display unit 34 displays an image based on thetomographic/Doppler image data. When a plurality of tomographic imagedata items are output from the tomographic image generating unit 30 intime sequence and a plurality of Doppler image data items are outputfrom the Doppler image generating unit 28 in time sequence, the imagecombining unit 32 generates the tomographic/Doppler image data in timesequence based on each image data item, and the display unit 34 displaysthe moving image based on the tomographic/Doppler image data generatedin time sequence.

The display unit 34 may display numerical values or graphs, for example,that represent the velocity measurement values, based on the numericalvalue image data output from the Doppler image generating unit 28 andinput to the image combining unit 32.

The above processing determines the velocity measurement value for eachof a plurality of received beams formed with respect to eachtransmitting beam. When any of a plurality of received beams formed forone of adjacent transmitting beams overlaps any of a plurality ofreceived beams formed for the other transmitting beam, the velocitymeasurement values for the overlapping received beams areweight-combined, and a combined measurement value is obtained. Thisapproach prevents an image based on the Doppler image data from beingdisplayed on the display unit 34 in a discontinuous manner in the screendirection. In color Doppler images, for example, generation of adiscontinuous region such as black dot defects at boundaries between animage region formed by one set of received beams and an image regionformed by another set of received beams can be reduced. Further, whenweight-combining the velocity measurement values for two received beams,the weighting coefficient for a received beam which is closer to atransmitting beam is set greater than that for a received beam which ismore distant. Generally, the shorter the distance between a receivedbeam and a transmitting beam corresponding to the received beam, thehigher the accuracy of measurement values based on ultrasound wavesreceived according to the received beam. Therefore, the weightedcombining as described above enhances the accuracy of the combinedmeasurement values.

In the above example, the combining/selecting unit 26 weight-combinesthe velocity measurement values for two overlapping beams.Alternatively, the combining/selecting unit 26 may select one of the twovelocity measurement values obtained for two overlapping received beams,based on a predetermined evaluation condition. A value representing theevaluation condition may be, for example, a variation level for aplurality of received data items from which the velocity measurementvalues have been obtained. More specifically, statistics representingthe degree of variation, such as dispersion or standard deviation, for Nreceived data items obtained based on ultrasonic pulses transmitted andreceived N times are used.

In this case, the velocity calculation unit 40 in FIG. 3 operates as avariation determining unit that determines, for each received beam, thevariation level concerning the amount that contributes to the velocitymeasurement value. Specifically, the velocity calculation unit 40 usesthe real part and the imaginary part of z(y, k)·z(y, k+1)* which issummed in the right side of Formula 2 to determine a neighboringtime-Doppler frequency fa(y, k) according to Formula 6 for each of k=1to N−1.

$\begin{matrix}{{{fa}\left( {y,k} \right)} = {\frac{1}{2\pi \; T}{\arctan \left\lbrack \frac{{Im}\left\lbrack {{z\left( {y,k} \right)} \cdot {z\left( {y,{k + 1}} \right)}^{*}} \right\rbrack}{{Re}\left\lbrack {{z\left( {y,k} \right)} \cdot {z\left( {y,{k + 1}} \right)}^{*}} \right\rbrack} \right\rbrack}}} & \left\lbrack {{Formula}\mspace{14mu} 6} \right\rbrack\end{matrix}$

The velocity calculation unit 40 determines the variation level for N−1neighboring time-Doppler frequencies fa(y, 1), fa(y, 2), . . . fa(y,N−1), and outputs the result to the combining/selecting unit 26. Thevariation level is defined by dispersion, standard deviation, and thelike, for the N−1 neighboring time-Doppler frequencies.

When the first received beam that belongs to a set of received beamsformed corresponding to the first transmitting beam and the secondreceived beam that belongs to a set of received beams formedcorresponding to the second transmitting beam overlap each other, thecombining/selecting unit 26 operates as a selection unit that selectsone of the velocity measurement value obtained for the first receivedbeam or the velocity measurement value obtained for the second receivedbeam, based on the evaluation condition for each velocity measurementvalue.

The combining/selecting unit 26 first determines selected measurementvalues v0 to v4 for the received beams R0 to R4 to be the same values asthe velocity measurement values, respectively, output from the Dopplerprocessing unit 24.

The combining/selecting unit 26 selects, of the velocity measurementvalue v(R5) obtained for the received beam R5 at the depth y=y0 based onFormula 3 and the velocity measurement value v(Q0) obtained for thereceived beam Q0 at the depth y=y0 based on Formula 3, a velocitymeasurement value with the smaller variation level, as a selectedmeasurement value v5. The combining/selecting unit 26 similarly selects,of the velocity value v(R6) obtained for the received beam R6 and thevelocity measurement value v(Q1) obtained for the received beam Q1, avelocity measurement value with the smaller variation level as aselected measurement value v6. The combining/selecting unit 26 similarlyselects, of the velocity measurement value v(R7) obtained for thereceived beam R7 and the velocity measurement value v(Q2) obtained forthe received beam Q2, a velocity measurement value with the smallervariation level as a selected measurement value v7.

This processing corresponds to the processing for determining, when thevariation level obtained for the received beam to be observed (the firstreceived beam) is smaller than the variation level obtained for thereceived beam to be combined (the second received beam), the weightingcoefficient for the received beam to be observed to be 1 in Formula 4.This processing further corresponds to the processing for determining,when the variation level obtained for the received beam to be observedis greater than the variation level obtained for the received beam to becombined, the weighting coefficient for the received beam to be observedto be 0. For example, when the variation level for the received beam R5is smaller than the variation level for the received beam Q0, theweighting coefficient w5 is 1. When the variation level for the receivedbeam R5 is greater than the variation level for the received beam Q0,the weighting coefficient w5 is 0.

The combining/selecting unit 26 similarly selects, of the velocitymeasurement value v(Q5) obtained for the received beam Q5 and thevelocity measurement value v(P0) obtained for the received beam P0, avelocity measurement value with the smaller variation level, as aselected measurement value v10. The combining/selecting unit 26 furtherselects, of the velocity measurement value v(Q6) obtained for thereceived beam Q6 and the velocity measurement value v(P1) obtained forthe received beam P1, a velocity measurement value with the smallervariation level, as a selected measurement value v11. Thecombining/selecting unit 26 also selects, of the velocity measurementvalue v(Q7) obtained for the received beam Q7 and the velocitymeasurement value v(P2) obtained for the received beam P2, a velocitymeasurement value with the smaller variation level, as a selectedmeasurement value v12. Finally, the combining/selecting unit 26determines selected measurement values v13 to v17 for the received beamsP3 to P7 to be the same values as the velocity measurement values outputfrom the Doppler processing unit 24, respectively.

The combining/selecting unit 26, based on the selected measurementvalues obtained for each position (each depth) in the y-axis directionand for each position in the x-axis direction, generates velocitymeasurement data correlated to xy coordinate values, and outputs the xycoordinate values to the Doppler image generating unit 28.

The processing described above selects, of two velocity measurementvalues obtained for two overlapping received beams, one with a smallervariation, and determines the selected velocity measurement value as aselected measurement value for the two received beams. The variationlevel indicates the degree of variation of a measurement value based onultrasonic pulses transmitted and received N times, and usually, as thevariation level decreases, the accuracy of the velocity measurementvalues increases. It is therefore likely that, of two velocitymeasurement values obtained for two overlapping received beams, the onewith the higher measurement accuracy is selected as a selectedmeasurement value.

One of two velocity measurement values obtained for two overlappingreceived beams may be selected based on the observing side transmittingand receiving distance and the combining side transmitting and receivingdistance. In this case, when the observing side transmitting andreceiving distance is smaller than the combining side transmitting andreceiving distance, the velocity measurement value obtained for thereceived beam to be observed is selected, whereas when the observingside transmitting and receiving distance is greater than the combiningside transmitting and receiving distance, the velocity measurement valueobtained for the received beam to be combined is selected. When theobserving side transmitting and receiving distance and the combiningside transmitting and receiving distance are equal to each other, eitherone of the two velocity measurement values is selected as desired.

In the above example, when two received beams overlap each other, thecombined measurement value or the selected measurement value is obtainedfor the overlapping two received beams. Alternatively, when two receivedbeams are in another predetermined positional relationship, the combinedmeasurement value or the selected measurement value may be determinedfor the two received beams. For example, when two received beams arewithin a predetermined distance range at a certain depth, such as whenthe distance on the x-axis at the depth of y=y0 is equal to or less thana threshold value δ, the combined measurement value or the selectedmeasurement value may be obtained for the two received beams.

The transmitting beams may be sector-scanned. The sector scanning refersto scanning for oscillating transmitting beams about a reference pointfixed for the probe serving as a center. FIG. 4 illustrates an examplepositional relationship between the transmitting beams and the receivedbeams when sector scanning is performed. In FIG. 4, an r-axis positivedirection is defined in the depth direction, and a θ-axis is defined inthe direction in which the transmitting beams oscillate. FIGS. 4 (a) to(c), which are arranged in the vertical direction for the convenience ofexplanation, show the transmitting beams and the received beams formedat the same depth with different time points.

FIG. 4 (a) illustrates eight received beams R0 to R7 formed at positionswith the depth r=r0 at equal angular intervals toward the r-axisdirection with a transmitting beam T0 being their center. FIG. 4 (b)illustrates scanning of the transmitting beam in the θ-axis positivedirection and forming a transmitting beam T1 in a direction differentfrom the direction of the transmitting beam T0. At positions with thedepth r=r0, eight received beams Q0 to Q7 are formed at equal angularintervals toward the r-axis direction with the transmitting beam T1being their center. FIG. 4 (c) illustrates scanning of the transmittingbeam in the θ-axis positive direction and forming a transmitting beam T2in a direction different from the direction of the transmitting beam T1.At positions with the depth r=r0, eight received beams P0 to P7 areformed at equal angular intervals toward the r-axis direction with thetransmitting beam T2 being their center.

The phase alignment and summation unit 22 illustrated in FIG. 1generates, for each of the ultrasonic pulses transmitted and received Ntimes for one transmitting beam, received data based on ultrasound wavesreceived along each received beam, and outputs each received data unitto the Doppler processing unit 24.

The Doppler processing unit 24 obtains a velocity measurement value foreach received beam and outputs the velocity measurement values to thecombining/selecting unit 26. When any of M received beams formed for oneof two adjacent transmitting beams and any of M received beams formedfor the other of the two adjacent transmitting beams overlap each other,the combining/selecting unit 26 combines the velocity measurement valuesobtained for the overlapping received beams.

As illustrated in FIGS. 4 (a) and (b), the received beams R5 to R7,among the received beams R0 to R7 formed with the transmitting beam T0being as their center, are respectively formed at the same positions asthose of the received beams Q0 to Q2, among the received beams Q0 to Q7formed with the transmitting beam T1 being as their center. Further, asillustrated in FIGS. 4 (b) and (c), the received beams Q5 to Q7, amongthe received beams Q0 to Q7 formed with the transmitting beam T1 beingas their center, are respectively formed at the same positions as thoseof the received beams P0 to P2, among the received beams P0 to P7 formedwith the transmitting beam T2 being as their center.

The combining/selecting unit 26 determines, concerning each direction inthe θ-axis direction at the depth r=r0 of the received beams R0 to R7,the received beams Q3 to Q7, and the received beams P3 to P7, a combinedmeasurement value by using the velocity measurement value according toFormula 3. Specifically, the combining/selecting unit 26 obtainscombined measurement values v0 to v17 for the 18 received beams to beobserved, which are the received beams R0 to R7, the received beams Q3to Q7, and the received beams P3 to P7, sequentially from the left.

The combining/selecting unit 26 first determines the combinedmeasurement values v0 to v4 for the received beams R0 to R4 to be thesame values as the velocity measurement values output from the Dopplerprocessing unit 24, respectively. The combining/selecting unit 26 thenobtains the combined measurement values v5 to v7 for the received beamsR5 to R7 to be observed according to Formula 4.

The combining/selecting unit 26 further determines the combinedmeasurement values v8 and v9 for the received beams Q3 to Q4 to be thesame values as the velocity measurement values output from the Dopplerprocessing unit 24, respectively. The combining/selecting unit 26 thenobtains the combined measurement values v10 to v12 for the receivedbeams Q5 to Q7 to be observed according to Formula 5.

The combining/selecting unit 26 further determines the combinedmeasurement values v13 to v17 for the received beams P3 to P7 to be thesame values as the velocity measurement values output from the Dopplerprocessing unit 24, respectively.

The combining/selecting unit 26, based on the combined measurement valueobtained at each position in the r-axis direction (each depth) and eachposition in the θ-axis direction, generates velocity measurement datacorresponding to rθ coordinate values, and outputs the data to theDoppler image generating unit 28. The Doppler image generating unit 28,concerning the velocity measurement data, transforms the rθ coordinatevalues to coordinate values for the display screen to thereby generateDoppler image data.

In the case of sector scanning, similar to linear scanning, one of twovelocity measurement values obtained for two overlapping received beamsmay be selected based on an evaluation value such as the variation levelfor each received data item, the observing side transmitting andreceiving distance, and the combining side transmitting and receivingdistance. Also, in place of combining the velocity measurement values orselecting one of the velocity measurement values when two received beamsoverlap each other (hereinafter referred to as combining/selecting),combining/selecting may be executed when two received beams are in otherpredetermined positional relationships. For example, combining/selectingmay be executed when two received beams are within a predetermineddistance range at a given depth. In this case, when the distance on theθ-axis at the depth r=r0 is a threshold value δ or less,combining/selecting is executed.

In either linear scanning or sector scanning, the combining of thevelocity measurement values when two received beams overlap each othermay include, in place of determining a weighting coefficient based onthe observing side transmitting and receiving distance and the combiningside transmitting and receiving distance, determining a weightingcoefficient in accordance with the variation level. For example, theweighting coefficient w for a received beam to be observed is determinedwithin a range of 0<w<0.5 when the variation level obtained for thereceived beam to be observed is greater than the variation level for thereceived beam to be combined. When the variation level obtained for thereceived beam to be observed is smaller than the variation level for thereceived beam to be combined, the weighting coefficient w is determinedwithin a range of 0.5<w<1. When the variation level obtained for thereceived beam to be observed is equal to the variation level for thereceived beam to be combined, w=0.5 is determined.

In the above embodiment, an example in which combining/selecting isexecuted for three sets of received beams is described. Morespecifically, in the above example, combining/selecting is executed forreceived beams on the right end side of one set of received beams andreceived beams on the left end side of an adjacent set of received beamson the right. Four or more sets of received beams may be used. In thiscase, similar to the case of three sets of received beams,combining/selecting is executed sequentially from the left such that oneor more received beams on the right end side of one set of receivedbeams and one or more received beams on the left end side of one set ofreceived beams to the right are combined or one or more received beamson one side are selected. Alternatively, combining/selecting is executedsequentially from the right such that one or more received beams on theleft end side of one set of received beams and one or more receivedbeams on the right end side of one set of received beams to the leftundergo combining/selecting.

REFERENCE SIGNS LIST

10 beam control unit, 12 transmitter unit, 14 probe, 16 transducerelement, 18 examinee, 20 receiver unit, 22 phase alignment and summationunit, 24 Doppler processing unit, 26 combining/selecting unit, 28Doppler image generating unit, 30 tomographic image generating unit, 32image combining unit, 34 display unit, 36 MTI filter processing unit, 38autocorrelation processing unit, 40 velocity calculation unit, T0 to T2transmitting beam, R0 to R7, Q0 to Q7, P0 to P7 received beam.

1. An ultrasonic diagnostic device, comprising: a transmitter unitconfigured to transmit ultrasound waves for each of a plurality oftransmitting beams formed at different positions or in differentdirections; a receiver unit configured to receive ultrasound wavesconcerning each of a plurality of received beams in each set of receivedbeams, the plurality of received beams being formed at differentpositions or in different directions, the each set of received beamsbeing formed corresponding to each transmitting beam; a Dopplerprocessing unit configured to determine a Doppler measurement value foreach of the received beams based on the ultrasound waves received by thereceiver unit; and a combining unit configured to combine, when a firstreceived beam that belongs to a set of received beams formedcorresponding to a first transmitting beam and a second received beamthat belongs to a set of received beams formed corresponding to a secondtransmitting beam are in a predetermined positional relationship, afirst Doppler measurement value determined for the first received beamand a second Doppler measurement value determined for the secondreceived beam, wherein the combining unit is configured toweight-combine the first Doppler measurement value and the secondDoppler measurement value, with weighting in accordance with a distancebetween the first transmitting beam and the first received beam or adifference in directions between the first transmitting beam and thefirst received beam, and a distance between the second transmitting beamand the second received beam or a difference in directions between thesecond transmitting beam and the second received beam, and the combiningunit is configured to set, in weight-combining, greater weighting forthe first Doppler measurement value or the second Doppler measurementvalue that is determined based on a smaller distance between thetransmitting beam and the received beam or based on a greater differencein directions between the transmitting beam and the received beam. 2.(canceled)
 3. An ultrasonic diagnostic device, comprising: a transmitterunit configured to transmit ultrasound waves for each of a plurality oftransmitting beams formed at different positions or in differentdirections, the transmitter unit configured to transmit ultrasound wavesa plurality of times for one transmitting beam; a receiver unitconfigured to receive ultrasound waves concerning each of a plurality ofreceived beams in each set of received beams, the plurality of receivedbeams being formed at different positions or in different directions,the each set of received beams being formed corresponding to eachtransmitting beam; a Doppler processing unit configured to determine aDoppler measurement value for each of the received beams based on theultrasound waves received by the receiver unit a plurality of times; anda combining unit configured to combine, when a first received beam thatbelongs to a set of received beams formed corresponding to a firsttransmitting beam and a second received beam that belongs to a set ofreceived beams formed corresponding to a second transmitting beam are ina predetermined positional relationship, a first Doppler measurementvalue determined for the first received beam and a second Dopplermeasurement value determined for the second received beam, and avariation determining unit configured to determine, for each of thereceived beams, a variation level based on an amount that contributes tothe Doppler measurement value, concerning the ultrasound waves receivedby the receiver unit a plurality of times for each of the receivedbeams, wherein the combining unit is configured to weight-combine thefirst Doppler measurement value and the second Doppler measurementvalue, with weighting in accordance with the variation level determinedfor each of the first Doppler measurement value and the second Dopplermeasurement value, and the combining unit is configured to set, inweight-combining, greater weighting for the first Doppler measurementvalue or the second Doppler measurement value for which the variationlevel is smaller value or the second Doppler measurement value having asmaller variation value.
 4. An ultrasonic diagnostic device, comprising:a transmitter unit configured to transmit ultrasound waves for each of aplurality of transmitting beams formed at different positions or indifferent directions; a receiver unit configured to receive ultrasoundwaves concerning each of a plurality of received beams in each set ofreceived beams, the plurality of received beams being formed atdifferent positions or in different directions, the each set of receivedbeams being formed corresponding to each transmitting beam; a Dopplerprocessing unit configured to determine a Doppler measurement value foreach of the received beams based on the ultrasound waves received by thereceiver unit; and a selecting unit configure to select, when a firstreceived beam that belongs to a set of received beams formedcorresponding to a first transmitting beam and a second received beamthat belongs to a set of received beams formed corresponding to a secondtransmitting beam are in a predetermined positional relationship, eithera first Doppler measurement determined for the first received beam or asecond Doppler measurement determined for the second received beam,based on an evaluation condition for each Doppler measurement value. 5.The ultrasonic diagnostic device according to claim 4, wherein theselecting unit is configured to select either the first Dopplermeasurement value or the second Doppler measurement value based on apositional relationship between the first transmitting beam and thefirst received beam and a positional relationship between the secondtransmitting beam and the second received beam.
 6. The ultrasonicdiagnostic device according to claim 4, wherein the transmitter unit isconfigured to transmit ultrasound waves a plurality of times for onetransmitting beam, and the Doppler processing unit is configured todetermine the Doppler measurement value for each of the received beamsbased on the ultrasound waves received by the receiver unit a pluralityof times, the ultrasonic diagnostic device comprising a variationdetermining unit configured to determine, for each of the receivedbeams, a variation level based on an amount that contributes to theDoppler measurement value, concerning the ultrasound waves received bythe receiver unit a plurality of times for each of the received beams,the selecting unit being configured to select either the first Dopplermeasurement value or the second Doppler measurement value based on thevariation level determined for each of the first Doppler measurementvalue and the second Doppler measurement value.